Remove unused shortHostname helper

Was added when PurgeSnapshots needed hostname-aware name parsing.
After adopting parseSnapshotName(snapshotID) from origin, the
helper has no callers.

internal/vaultik/snapshot.go

@@ -728,19 +728,6 @@ func (v *Vaultik) confirmAndExecutePurge(toDelete []SnapshotInfo, force, quiet b
 	return nil
 }
 
-// shortHostname returns the configured hostname stripped of its domain suffix.
-// This matches the hostname-prefix used when building snapshot IDs.
-func (v *Vaultik) shortHostname() string {
-	hostname := v.Config.Hostname
-	if hostname == "" {
-		hostname, _ = os.Hostname()
-	}
-	if idx := strings.Index(hostname, "."); idx != -1 {
-		hostname = hostname[:idx]
-	}
-	return hostname
-}
-
 // VerifySnapshot checks snapshot integrity
 func (v *Vaultik) VerifySnapshot(snapshotID string, deep bool) error {
 	opts := &VerifyOptions{Deep: deep}